20 OBJECTIVES 
This multi-disciplinary study attempts to 
evaluate the capability of the ERS-1 synthetic 
aperture radar data for providing basic information in 
assessing the adverse effects on the environment 
brought about by the eruption of Mount Pinatubo. 
Using single and multitemporal ERS-1 data sets, the 
study focuses on general, thematic and 
methodological objectives by utilizing the unique side 
geometry of ERS-1 radar and terrain surface 
roughness and moisture content. The general 
objectives include the development of appropriate 
relationships between ERS-1 synthetic aperture radar 
backscatter and various land-based surface features 
particularly lahar-affected agricultural and residential 
areas; the assessment of the usefulness of ERS-1 
radar data as a major source for acquiring landcover 
information over perennially cloud-covered lahar- 
affected areas surrounding Mount Pinatubo, with 
particular focus on the capability of ERS-1 data in 
improving landcover change detection analysis such 
as the changing river patterns due to mudflow; and 
the development of the capability to create data 
products from multi-temporal ERS-1 radar data 
sources. 
The thematic objectives include lahar extent 
detection and mapping for GIS-based predictive 
modelling of hazard risks and follow up of erosion 
and evolution of drainage networks. The 
methodological objective includes the analysis of the 
synergy and complementarity of radar and visible- 
infrared data for detecting geomorphic and landcover 
features. 
30 STUDY AREA 
The study area is located in the northern part 
of the Philippines, on the central part of its largest 
island, Luzon, and is centered at latitude 15° 37' N 
and longitude 121° 25' E and includes the geographic 
territory known as Central Luzon bounded on the 
west by the South China Sea, on the north by the foot 
of the Caraballo mountains, on the east by the Sierra 
Madre mountains and on the south by the Manila 
Bay. The areas of interest include two cities and 
twenty-eight municipalities located in the provinces 
of Zambales, Pampanga, Tarlac, Nueva Ecija and 
Bulacan, which are all potential pathways for the 
volcanic mudflow, and covering an estimated half 
million hectares. 
It also includes the immediate vicinity of 
Mount Pinatubo volcano which is now about 150 
- processing techniques. 
439 
meters lower than its pre-eruption elevation of 1,750 
meters above mean sea level and the floodplain which 
have undergone significant landscape alterations after 
serving as lahar catch basins. There are two main 
physiographic regions, namely, the Zambales 
mountain range (an area of orogenic uplift, or 
mountain formation, within which is a north-south 
trending volcanic arc) and, to the east of the volcano, 
the Central Luzon basin, an 80-kilometer sediment- 
filled depression consisting primarily of volcanic- 
derived materials such as gravel, sand and clay. 
Eight major river systems surround the volcano. On 
the west, the Santo Tomas, Maloma and Bucao Rivers 
drain directly into the South China Sea; and on the 
east, the O'Donnell River flows north into the Tarlac 
River and the Sacobia-Bamban, Abacan, Pasig- 
Potrero and Gumain-Porac Rivers merge with the 
Pampanga River thence into the Manila Bay (Figure 
2). 
4.0 ERS-1 RADAR DATA SETS 
Five sets of ERS-1 SAR Precision images 
(C-band, 5.6-cm wavelength, 23-degree incidence 
angle) obtained along two adjacent orbital strips at 
35-day intervals in the descending mode were 
provided by the European Space Agency through the 
EC-ASEAN Radar Research Pilot Projects. ERS-1 
radar frame 3303 covers both strips obtained on the 
following orbits and dates: two sets for the western 
portion (orbit 10354 taken July 9, 1993, and orbit 
10855 taken August 13, 1993) and three sets for the 
eastern portion (orbit 10583 taken on July 25, 1993; 
orbit 11084 taken on August 29,1993 and orbit 11585 
taken on October 3, 1993. 
5.0 LANDSAT TM DATA SETS 
The optical remotely-sensed data consist of 
one set of Landsat Thematic Mapper image, path/row 
116-050, acquired on April 2, 1993. 
6.0 METHODOLOGY 
The initial results of this investigation into 
the capability of the ERS-1 SAR data were generated 
by combined visual interpretation and digital image 
To understand how lahar 
ground characteristics are featured in ERS-1 SAR 
imagery, two successive acquisitions at 35-day 
intervals over the western portion of the study area 
were examined initially together with information on 
significant lahar events that occurred during the 
period furnished by the Philippine Institute of 
Volcanology and Seismology (PHIVOLCS). The 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996